[piciu256]

We all know (most of us anyway) that ebikes have better bump absorbtion, thanks to the higher sprung to unsprung mass ratio, keeping that in mind I just had a "crazy" idea, would it make sense to add let's say 3 kilos to the down tube of my frame for bike park laps, as in riding where I don't care about weight at all? Would that make enough of a difference?
I recall someone testing the idea for downhill racing, but don't remember the results, or if the testing was so specific.

 

[plummet]

No!
Lighter is better unless it starts to hinder performance by using weaker, flexier parts.

You will get far, far better performance increase by tyre selection and suspension improvements.

 

[piciu256]

Sorry M8, I beg to disagree, lighter is not better for bump compliance and I don't do tricks mid air so that doesn't matter for me either, I assume already having good suspension and tire choice, just a theoretical possibility to gain a bit more performance with little effort, for when I need it (long days in parks) and can live with more weight (I don't have to carry it uphill)

 

[ocnLogan]

Sorry M8, I beg to disagree, lighter is not better for bump compliance and I don't do tricks mid air so that doesn't matter for me either, I assume already having good suspension and tire choice, just a theoretical possibility to gain a bit more performance with little effort, for when I need it (long days in parks) and can live with more weight (I don't have to carry it uphill)

I haven’t looked into it extensively. But as far as I know “someone” (Chris porter? About 5-10ths ago maybe?) tested it for a while on the World Cup downhill circuit.

And importantly, they tested it. And didn’t stick with it.

And if the World Cup level is good at anything, it’s doing “anything” that is faster, even if it is unconventional.

The principle of the ratio of sprung, and unsprung weight is solid. So I’m sure adding weight is of benefit in certain circumstances (straight plowing most likely). But if people have tried it and it’s still not a “thing”, then it must have some downsides elsewhere, enough to be a net negative.

I’m no weight weenie, as I ride a 36-37lb bike everywhere (it’s my only bike). But I think I’m probably in the camp of “a Bike should weigh as much as it needs to be durable and reliable enough for its use criteria, but don’t add much/any more past that”.

That’s said, it’s your bike. So, go for it and see what you think of the before and after .

 

[piciu256]

I will probably play around with the idea, wouldn't cost me much if anything to strap some weights to the frame, was just wondering if a couple of kilo would make a noticeable difference, 3kg is all that I can imagine realistically adding to a bike without custom parts, probably less.
Technically the rider is also sprung mass, but we're not rigidly connected to the bike, I'm mostly thinking about reducing shock loading of arm joints, as I have an issue right there.

 

[BansheeRune]

We all know (most of us anyway) that ebikes have better bump absorbtion, thanks to the higher sprung to unsprung mass ratio, keeping that in mind I just had a "crazy" idea, would it make sense to add let's say 3 kilos to the down tube of my frame for bike park laps, as in riding where I don't care about weight at all? Would that make enough of a difference?
I recall someone testing the idea for downhill racing, but don't remember the results, or if the testing was so specific.

Rubbish!

 

[piciu256]

Have you ridden an ebike, or even a motorbike for that matter? Or even more extreme, a car, have you ever held a car shock in your hands? The damping and friction is so high that it's hard to compress it by hand, and still, small bumps are not transferred at all, I know it's an exaggeration, but the idea is the same with bikes.
For all those thinking in lines of "any weight added to a bike is pointless", please don't bother replying to this thread, there are plenty of religious pointless weight saving threads out there already, that's not it, I know my physics and I know that a few kilo added down low wouldn't hurt the bikes performance in the slightest, I don't race XC, nor do most people, so I don't care about weight too much, I don't care that it's not fashionable.

 

[the-one1]

Why ask of you're already set on doing it?

 

[BansheeRune]

Frankly, if I gave a rat's ass about weight, I would not be riding a plus bike let alone, a Wildcat! Since my bike is not plastic, there is nothing about "fashion" but plenty on the topic of performance based upon what matters, rider weight, bike fit and how the suspension works with said rider under the conditions in use and practical application.
Proper design of a suspension SHALL be based upon design load for operation before the blueprint is is sent to the plotter. Pretty basic concept from the inception.

If I had to add ballast to make the bike function, it is inherently flawed from the start!

Would adding a few kilos down low force me to adjust the shock preload, compression and rebound? Obviously! As a matter of fact, I may well have to rework the shock valving and blowoff valve as well!

 

[piciu256]

You misunderstand me, I asked a theoretical question and got people feeling offended that someone may want to make a bike heavier, just saying that if you don't have anything to add, you may vote in the poll, but don't bother replying. I'm just looking for if someone tried this already and found, for example, that the difference is not worth the effort, like I found with reducing unsprung rear wheel mass by going to a single speed setup for example.

 

[piciu256]

If I had to add ballast to make the bike function, it is inherently flawed from the start!

Would adding a few kilos down low force me to adjust the shock preload, compression and rebound? Obviously! As a matter of fact, I may well have to rework the shock valving and blowoff valve as well!

You misunderstand also, it's not about making it work at all, just about potentially squeezing out just that tiny bit more performance with no added cost, need to change the settings a little won't matter, I'll be running air up front and air or coil in the back, I'm not so particular as to change spring rate by 3% because the riding setup weight changed by 3%, I'm more of a set it and forget it kind of guy. Also, for park I won't be running a pack or water so I guess it evens itself out somewhat.
I like a good discussion.

 

[BansheeRune]

You misunderstand me, I asked a theoretical question and got people feeling offended that someone may want to make a bike heavier, just saying that if you don't have anything to add, you may vote in the poll, but don't bother replying. I'm just looking for if someone tried this already and found, for example, that the difference is not worth the effort, like I found with reducing unsprung rear wheel mass by going to a single speed setup for example.

I for one take no offense to the question but state the obvious, that the suspension will need adjustment by changing the load applied in use.
I'll give an example... I have cancer and am losing weight at an alarming rate! Due to this change in load, I have changed the various attributes of the fork and shock to keep the form, function and performance where I care for it to be. With my weight change from diagnosis to now, it is a significant change in load. 23k is a large loss of weight! Now there is a significant difference by 20k.

Therefore, adding weight will serve no purpose other than to change the setup to accomodate that vs. the actual load applied.9

 

[piciu256]

Nah, let's assume you adjusted all settings accordingly for the change in weight, damping stays relatively the same, so does the spring rate, (sag etc.) but instead of a 2kg front triangle it weighs 5, pretty much doubled the rigidlyounted sprung mass, so potentially reduced the initial impact shock transferred to your hands by half (same force, 2x the mass= 2x lower acceleration), see what I mean?
All I want to determine is if the theory translates to real life, I've ridden an ebike and seen they ride smoother, but it wasn't a 1:1 comparison, as in different suspension components and kinematics and far from the same settings.

 

[MTB_Underdog]

You also need to take into account that any weight you add needs to be slowed down and to change direction, so the bike will do those things less well. Just something to think about.

 

[mtnbkrmike]

Hahaha! I see I’m not the only one not able to sleep!

I will offer a counter point, coming from a guy who racks up a lot of mileage year after year, but who has little to no business being involved in this discussion due to a complete lack of technical expertise from which to draw.

I have continually noticed this sprung/unsprung weight phenomenon on my e-fattie. As recently as yesterday! It’s a hardtail but nonetheless. I love riding it for exactly what the OP describes. For low speed, straight line, ground hugging bump absorbing bliss, it rules. I don’t know if it’s the tires or the dehydrated unicorn poop Norco sprinkled inside the top tube, but I am convinced there is something very special going on, and I’m pretty sure the magic is largely created by the added weight.

 

[Nat]

Here you go:

Add weight, go faster — Orange bucks the lightness trend

Removable weights give options to adjust sprung weight

www.bikeradar.com

 

[piciu256]

I love slow tech but also do higher speed stuff, that's why I'm upgrading from an aggressive trail bike to something more forgiving atm, I'm pretty sure added sluggishness from 3kg (I weigh 55kg kitted up, bike is net 15kg so that would make it up to 18kg with added weight, or just over 4% difference) would not be noticeable, that's coming from me not feeling any difference with or without a 0.7l water bottle.

ps. for me it's the middle of the day, however off riding season cause I despise mud, so good time for potentially pointless discussions 😜

 

[cookieMonster]

If all-out speed is your goal, then this approach will have diminishing returns. How do I know? I used to ride a 45 pound DH bike. Yes, it was stable in the rough. However, even in a bike park where it is predominantly steep and, well, downhill, the direction changes are what kill you on those heavy bikes. When I ditched the Monster T fork and replaced it with a 3 pound lighter Marz. 66 RC2X my times immediately got faster. That brought the bike down to around 42 pounds. Additionally, I also found that the ridiculously burly Intense 2.7 tires, when replaced with lighter casing 2.5s also sped me up considerably. Fast forward a decade and I found myself on a 35 pound enduro bike, with better geometry, suspension that was just as good, and guess what, my times got remarkably better.

I've ridden my dad's E-bike too. I would guess it weighs around 45 pounds as well. Great geometry and suspension. Guess who wins on the downhills when we ride together?

I come from a moto background as well. Apples to oranges. Yes, a motocross/off-road dirt bike can plow through chunder like nothing else, yet it has the brakes and traction to shut it all down, and then immediately rocket out of corners via 50+ horsepower. On tight, technical mountain bike trails, a nimble enduro bike or even modern DH bike can often negotiate that kind of terrain faster. I know there's trails I ride where I wouldn't want to be on a moto at all -- it is far too tight for such a big machine.

 

[Nat]

I'm mostly thinking about reducing shock loading of arm joints, as I have an issue right there.

Your idea of adding weight wasn’t totally “out there” but I think ultimately tuning your suspension is what you’ll want to do. It just costs more.

 

[piciu256]

Tuning I'll play around with when I have the bike, it'll cost a lot of effort but I'll be starting from a good baseline already, so I'm not too worried about that, what you have to remember though is that it's not possible to have zero friction in the system, so I looking at ways of reducing the impact from said friction etc.
The particular issue I experience in not very common, but I found a couple of people who have it too, it doesn't seem to be excercise or setup related, I myself don't get arm pump at all, I don't get the chance to really, cause my finger joints complain pretty quickly if I try to do a complete 10 minute run with big holes and braking bumps, hoping more suspension travel (lower spring rate) will help, but looking at other ways to help if it won't be enough.
Just riding smooth trails would resolve the issue completely, but where's the fun in that, and as said in the BR article (thanks for the link btw., wasn't able to find the damned thing) the bike feels more planted with more sprung weight, I like this idea, cause I'm more of the "leave the ground only when I feel like it" kind of rider.